1. Field of the Invention
The invention relates generally to communications in a wireless network. More particularly, various embodiments pertain to determining the size of a paging area in a wireless network supporting broadband wireless communications.
2. Background Art
Various broadband wireless communications standards such as WiMAX (e.g. the Institute of Electrical and Electronics Engineers (IEEE) 802.16e-2005 standard, released Feb. 28, 2006) incorporate the concept of a “paging group” (PG). In a wireless network supporting such a standard, a base station (BS) servicing a particular geographic area may belong to a paging group of one or more BSs, where the respective geographic areas of the one or more BSs define a “paging area” of the paging group. During an active call session, a mobile station (MS) serviced by the wireless network may be registered with a particular BS of the geographic region in which the MS operates.
In the absence of an active call session, the MS may switch to operating in an idle mode to conserve battery power. In idle mode, the MS may relinquish all of its connections and states associated with the base station (BS) with which it was last registered. While operating in idle mode, an MS alternates between a period of listening for paging messages, known as “paging listen interval” (PLI), and a period during which MS powers off its radio interface, known as “paging unavailable interval” (PUI).
The paging group in which an idle MS resides may be administered by a paging controller (PC). The wireless network may only maintain the current PG of an idle mode MS. When an MS enters an idle mode, a PC, referred to as anchor PC, may create an entry in its database noting the PG where the MS is initially located. The anchor PC of an idle mode MS may store the information about the said MS in idle mode. At different times in a network, different MSs in idle mode may have different anchor PCs. Each anchor PC may store information about one or more MSs in idle mode. When the MS moves from one PG to another, it may update the location with the anchor PC. When an idle mode MS moves away from its current PG and enters a new PG, its location information may be updated. This way, the idle MS may be tracked by the wireless network at the granularity of paging group, as opposed to a non-idle MS which may be tracked at the granularity of a BS. The network may use the approximate location information of an idle mode MS to locate and set up new connections with it.
Whenever required, the MS may be precisely tracked to its associated BS by sending a broadcast message known as Mobile Paging Advertisement (MOB-PAG-ADV) message to at least some BSs that comprise the MS's current PG. When the wireless network wants to locate an idle-mode MS, or has incoming data buffered for it, or for administrative purposes, the PC may initiate paging the MS. When a PC initiates paging for the MS the BSes of MS's PG in turn may broadcast MOB-PAG-ADV messages on the air-link. If the MOB-PAG-ADV is sent during the PLI of the MS, then the MS is expected to receive the page and perform network re-entry or location update in response to the page if it is alerted to do so.
Both air-link signaling messages (e.g., the respective MOB-PAG-ADV messages broadcasted by the BSes in the PG and messages exchanges between the MS and its serving BS during network re-entry) as well as backbone signaling messages (i.e., messages exchanged between various combinations of an MS, a BS, a PC, and various other network entities) may be used during a paging operation. The generation, transmission, reception and/or processing of air-link signaling messages and/or backbone signaling messages are examples of processes required to support paging groups which result in consumption of resources of the wireless network. Limited network resources may result in a limited ability to implement paging groups and/or may otherwise impact wireless network performance.